双圆弧齿轮泵流量特性影响因素数值模拟

目的：分析新型双圆弧齿轮泵内部流场脉动特性的影响因素，采用合理参数以提高齿轮泵输出效率。方法：建立齿轮泵的二维流场仿真模型，采用计算流体力学软件Fluent进行仿真分析，研究不同齿顶间隙、不同齿轮偏心距、负载及转速对齿轮泵出油口瞬时流量、流量脉动、流场特性的影响。结果：随着齿顶间隙增大，齿轮泵出口流量逐渐减小，当齿顶间隙为0.09 mm时，出口流量脉动系数最小为0.135，为该结构参数下齿轮泵最佳齿顶间隙；受负载压力和转速的影响，齿轮泵中心轴线产生偏差，随着齿轮泵转子中心轴线偏心距增加，齿轮泵出口流量逐渐增大，当偏心距为0.05 mm时，齿轮泵出口流量比无中心偏差时增加了5.09%，提高了流量输出。结论：齿轮泵流量特性主要影响因素为转子转速和齿顶间隙，中心偏差的影响较小。     

基于离散元法的螺旋喂料器流量计算修正

针对螺旋喂料器实际流量检测值与传统计算式计算值相差较大的问题,采用响应面试验对螺旋喂料器的流量计算式进行修正。考虑到实际试验的复杂性,采用离散元仿真流量值与计算式计算值的比值作为响应,以对流量比值影响显著的螺距、转速、管径为试验因素设计响应面试验,得到3个因素与响应值之间的二阶回归方程,由此进一步得到螺旋喂料器的流量计算式。为进一步验证修正后流量计算式的可行性,根据设计要求,用SolidWorks软件建立三维模型并进行仿真分析,发现仿真所得流量值为1.258t/h,与修正式计算所得流量值1.210t/h的误差为3.97%,表明了流量修正计算式的合理性。     

狭缝式熔体微分电纺流量控制与射流均匀性研究

采用自主设计的狭缝式熔体微分静电纺丝装置纺聚丙烯（PP）材料,研究了进料时挤出机转速与流量的关系以及流量大小对于出料均匀性的影响．并探究了不同流量下的纺丝射流效果。试验结果表明：PP料流量随转速的增大而增大,当转速达到18r／min时,出料流量基本不变,此时料流量为1．74g／min,出料均匀性好,不随流量变化而变化;在纺丝电压45kV,电极板距离90mm,纺丝温度230℃的工艺条件下,当转速为12r／min即流量为1．14g／min时,纺丝射流效果最好。     

基于质量流量法的透气度流量盘测量方法的建立与应用

为解决体积流量法在测量透气度流量盘时容易受环境因素影响、流量盘两端压差不稳定等问题, 基于质量流量法建立了一种透气度流量盘测量方法。该方法采用质量流量端子与控制器相结合的方式获得流量盘的质量流量, 并通过计算将质量流量转换为体积流量;基于LabVIEW软件搭建控制系统, 实现对流量盘两端压差的自动反馈调节, 将压差稳定在设定范围内;采用不同规格流量盘对该方法的重复性和稳定性进行测试, 并与体积流量法和国际共同实验进行对比。结果表明:①质量流量法与体积流量法相比, 二者测量结果的变异系数集中分布在0.2%左右, 相对极差分布在1%左右, 具有相近的重复性和稳定性;②质量流量法与国际共同实验相比, 二者测量结果的变异系数整体分布在0.2%左右, 相对偏差多数分布在1%左右, 最大相对偏差为1.91%, 具有较好一致性。该方法能够对流量盘实现稳定、准确测量, 并为提高测量装置的自动化水平提供支持。      

高浓漂白塔底稀释区旋转喷射管数值模拟

通过Fluent的Realizable κ-ε湍流模型以及多重旋转坐标系(MRF)技巧,对高浓漂白塔底稀释区旋转的直形和纺锤形两种喷射管进行了正反向几种转速的数值模拟,并对其各个出口的核心速度进行了采集和分析,然后利用粒子图像测速仪(PIV)对该模型进行了验证.结果表明,直形喷射管反向旋转转速10 r/min左右时,其各个出口的速度差值较小;纺锤形喷射管在正向旋转转速50 r/min下,其各个出口的速度差值最小;低转速的旋转喷射管在这两种条件下均可以视为等速喷射.用Realizable κ-ε湍流模型以及MRF技巧对旋转喷射水管进行数值计算和分析是可靠的.     

基于ADAMS的减速器仿真分析

本文首先利用三维软件PRO／E建立了某减速器的三维实体模型,并人为设置齿形误差故障,然后导入ADAMS建立了虚拟样机模型,本文将分别对齿轮间施加齿轮副约束和碰撞接触（contact）两种情况进行仿真,最后对仿真结果进行分析比较,从而证明了在齿轮间施加碰撞接触（COntact）进行仿真分析的可行性。     

新型偏心蠕动式转子泵的特性及流量分析

文章针对清洗机设备的要求和特点,提出了一种新型转子泵———偏心蠕动式转子泵,阐述了其工作原理和性能特点;用解析数学的方法推导出该泵的平均流量和瞬时流量公式;并用MATLAB软件拟合了瞬时流量曲线;计算了该泵的流量脉动率。通过对泵的分析研究,表明该泵具有结构紧凑,流量小,排出压力高,一定流量脉动的特点。该泵作为清洗机用泵,具有广阔的应用前景。图7参8     

行星机构式齿轮泵的性能分析

对行星机构式齿轮泵的组成原理、排量、瞬时流量、受力情况进行了分析，推导出了新型齿轮泵的几何排量、瞬时流量的计算公式，得出了减小流量脉动的齿数选择原则，为研究开发轻化工行业输送高粘度液体的新型齿轮泵提供了设计依据。     

燃油管道式烘丝机(HXD)燃烧炉系统的改进

燃油管道式烘丝机燃烧炉系统存在温度控制精度差、故障率高、柴油消耗大等问题,为此,对燃烧炉柴油管路系统进行了改进,将燃烧炉温度由单回路控制改为串级控制,根据柴油流量,通过检测燃烧炉尾气化学成分含量,对助燃空气风量进行自动调节,使助燃风机风量与柴油流量保持在最佳比例.应用效果表明,改进后工艺气流温度的响应速度和控制稳定性均有显著提高,燃烧炉的火焰信号增强且稳定.柴油管路系统运行可靠,点火失败或熄火故障次数由原来的2次/月以上减少为0,生产换牌时降低工艺气流温度30℃所需时间由20 min减少到10min左右,降低了柴油消耗,提高了生产效率.     

弹体双旋轮强力旋压的旋压力算法及仿真模型建立

针对双轮强旋提出一种基于轧制力的旋压力计算方法,克服传统旋压力计算时对金属堆积的忽略而造成的误差,通过电测法工艺实验验证,该算法准确有效。并以该算法为基础建立模型进行弹体的旋压仿真实验,用以对弹体的尺寸精度进行分析。该仿真经工艺实验进行了验证。实验结果表明:在弹体毛坯为20号钢,减薄量为10.6%,主轴转速为50r/min,进给量为3mm/r的情况下,仿真实验结果与工艺实验结果基本一致。     

立式屏蔽泵水力性能的数值模拟与分析

为研究SPG50-200型立式屏蔽泵的水力性能,给优化过流部件的结构设计提供基础,采用CFD分析软件对屏蔽泵的内部流动进行了数值模拟。给出了三维造型方法和流场分析方法,分析了泵内流体的速度和压力的分布特性。并基于流动模拟结果预测了水力性能,将计算结果与实验曲线进行了对比,研究了蜗壳断面形状对泵性能曲线的影响．介绍了屏蔽泵的应用前景。研究结果对泵的性能改进有一定指导意义。图11表1参9     

The control of milk flow through the teats of dairy cows.

The effects of teat smooth muscles and pulsation on the control of rate of milk flow have been investigated in two split udder experiments during machine milking of dairy cows. When two teats were milked without pulsation, the peak flow rate was reduced by .132 kg/min for these teats and by .107 kg/min for the other two teats, which received good pulsation. Both of these reductions were statistically significant. This suggests that there is systemic control of the teat sphincter muscle. When systemic muscle control was removed by treatment with clenbuterol, a beta-agonist, all flow rates increased. However, when the proportion of the pulsation cycle for which milk flow can occur was considered, the actual flow rate for teats milked without pulsation was approximately 36% lower than that for teats milked with pulsation. This was independent of clenbuterol treatment, suggesting that this local control is independent of overall muscle tone.     

Evaluation of an experimental milking pulsation system for effects on milking and udder health

This study was to test whether cows milked by an experimental pulsation method differed from cows milked with conventional pulsation milking in somatic cell count (SCC), intramammary infections (IMI) defined by milk bacteriological culture results, teat end condition, or milk flow rate. The study design was a 1-yr trial with a completely randomized block crossover. Holstein cows were blocked into 15 pairs of contemporaries. Both cows from each pair were milked with experimental pulsation and with conventional pulsation for 6 mo, in reverse order from each other. The SCC (217,000/ml) of experimentally milked cows was not significantly different from SCC of conventionally milked cows (175,000/ml). Mean milk flow rate was 5.2 lb/min (2.4 kg/min) for experimentally milked cows and 5.3 lb/min (2.4 kg/min) for conventionally milked cows, not significantly different. Differences among the experimentally and conventionally milked cows, respectively, in new (13.5 and 12.7%), chronic (12.9 and 8.9%), and negative (73.6 and 78.4%) quarter culture results were not significant. New IMI per 100 d of lactation were 1.50 and 1.46, and chronic IMI per 100 d were 1.85 and 1.27, for experimentally and conventionally milked cows, respectively. These IMI rates were not significantly different between pulsation types. There were more new Staphylococcus aureus IMI associated with conventional pulsation, but overall cases of Staph. aureus were similar between the two types of pulsation. Teat end scores for the experimentally and conventionally milked cows, respectively, were good (6.5 and 11.7%), intermediate (68.2 and 66.9%), and poor (25.3 and 21.4%), not significantly different. These results support previous studies, which have found that except for complete failure of pulsation, differences in pulsation characteristics apparently have little effect on milking and udder health.     

行星齿轮减速器均载性能动态的优化设计

基于遗传算法搜索技术以及行星齿轮传动系统的弯扭耦合振动模型,完成某2K-H型行星齿轮减速器动态均载性能的优化设计。通过行星齿轮传动系统动力学响应的数值计算,确定对减速器均载性能影响较为显著的几个设计参数,结合工程中方便修改实现的原则,从中选择内、外啮合副的齿侧间隙作为优化设计变量。根据工程中齿侧间隙的许可取值范围,确定设计变量的搜索区间。经过遗传算法的搜索,最终获得一组内、外啮合副的最优齿侧间隙组合,数值试验证实在该组参数组合下行星齿轮减速器的均载性能有了明显改善。     

不完全齿轮横动机构对静电纺丝膜均匀性的改善作用

针对多针头式静电纺丝产品横向均匀度较差的技术缺点,提出一种基于不完全齿轮齿条机构的新型线性模组结构;该结构能够实现往复式线性运动,可实现纺丝头的连续匀速横动,运行平稳、简单可靠,且不需要控制系统。该机构由一个主动不完全齿轮和一个从动双侧齿条框组成,由于齿轮齿条传动具有恒定传动比的特性,使得主动不完全齿轮的连续单向转动转化成从动双侧齿条框的匀速往复直线运动。这种机构应用于多针头静电纺丝的实验结果论证了其功能性、有效性和可靠性,可使电纺膜的横向均匀度从32.2%降低到2.7%,纵横向强力比也由2.05变为1.03。     

大豆油氢化反应釜数值模拟及工艺优化

以一级大豆油为液相、Pt/C催化剂为固相,釜体为圆柱体,釜体高度为180 mm,内径为120 mm,液面高度为130 mm,利用FIUENT软件对大豆油氢化反应釜进行液固两相数值模拟,发现倾斜式搅拌桨距反应釜底部高度80 mm、桨叶直径40 mm、搅拌速率300 r/min时流体流动及催化剂分布最佳,并以模拟的主要参数制备了高压反应釜。高压反应釜内一级大豆油添加量90.0 g、Pt/C催化剂添加量0.15%(m/m),充入8 MPa的CO2气体,后充入H2保持反应釜内总压为12 MPa,通过优化得出最佳反应温度97℃、反应时间87 min、搅拌速率285 r/min时,氢化后大豆油的碘值为79.50 g I2/100 g,说明模拟准确,为展示大型设备油脂氢化过程提供理论依据。     

Application of turbulent pulsating flows to the bacterial removal during a cleaning in place procedure. Part 1: Experimental analysis of wall shear stress in a cylindrical pipe

The effects of pulsating turbulent flows on wall shear stress components were investigated in a straight pipe using the non-intrusive electrochemical method. Experiments were made using a new pulsation generator system which allows high amplitude pulsations in addition to a perfect stability of the installation. Maximum pulsation frequency equal to 2.86 Hz is used, above which fluid inertia dominates over most part of the flow field.Analysis showed that pulsating flows induce an increase of local velocity gradient at the wall pipe. This result is explained by the periodic renewal of the boundary layers. Spectral analysis showed high increasing rates of the fluctuation energy for the different pulsating conditions in comparison with a steady flow. The tested condition involving a recirculation flow induced a modification in the energy dissipation cascade, which can be explained by the redistribution of eddies size near the wall.     

Influence of milk flow rate on new intramammary infection in dairy cows

In a series of short-term experiments cows were subjected to exaggerated bacterial challenge and accentuated milking machine conditions known to predispose to new mammary infection. The incidence of new intramammary infection was significantly greater in quarters with peak flow rates greater than 1.6 kg/min whether they were exposed to impacts (P less than 0.05) or milking without pulsation (P less than 0.001). The infection rates were much lower (P less than 0.001) in quarters milked with 'pulsation and shields' to protect against these two machine factors. Despite this, quarters with peak flow greater than 1.6 kg/min still showed a 12-fold increase in mastitis incidence compared with quarters with peak flow less than 0.8 kg/min. Rates of milk flow have increased dramatically in the last 40 years through selection and breeding: whole udder peak flow rates in heifers have doubled from 1.9 to 3.8 kg/min. Increased emphasis, therefore, should be placed on hygiene, husbandry and milking techniques to minimize bacterial numbers at teat ends to control mastitis as the drive for higher flow rate and yield make cows increasingly more susceptible to infection. These results suggest that the benefits of reduced infection rate from mastitis control are significantly underestimated since animals are now considerably more susceptible than 40 years ago.